1. Field of the Invention
This invention relates to color photographic elements and more particularly to improved color photographic elements having a significant reduction in granularity.
2. Description of Related Art
Color photographic silver halide elements are well known in the photographic art. Such elements are described in, for example, Research Disclosure, December 1989, Item No. 308119 and the references listed in this publication. (Research Disclosure is published by Kenneth Mason Publications Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire PO10 7 DQ, England.)
Silver halide color photographic materials described in U.K. Specification No. 818,687 have improved speed characterized in that the sensitive layer nearest to the support is a composite layer comprising two separate coatings of silver halide emulsions containing non-diffusible color formers which on color development yield images of the same or substantially the same color, the emulsions being sensitized to light of the same waveband.
U.K. Patent Specification 923,045 discloses a color photographic multilayer material having at least two light-sensitive silver halide emulsion layers. The layers contain colorless color couplers resistant to diffusion and capable of forming after imagewise exposure upon development with a color developer a colored image of substantially the same color, the two layers being sensitized to the same region of the same region of the visible spectrum but having different sensitivity. The more sensitive of these layers produces a color image of lower color density upon development than the less sensitive layer wherein the color coupler concentration in the more sensitive layer is 10-50 percent of the color coupler concentration in the less sensitive layer.
U.S. Pat. No. 3,843,369 discloses a multi-layer color photographic light-sensitive material, prepared using cyan-, magenta- and yellow-forming emulsion layers, each layer being divided into at least three emulsion layers sensitive to the same spectral region of visible light. Improved granularity of the dye image formed in each of the emulsion layers and also that of the overall image is obtained.
U.S. Pat. No. 4,184,876 discloses a photographic silver halide multi-layer color material having at least one blue-sensitive silver halide layer, at least two green-sensitive silver halide emulsion layers having different speeds and at least two red-sensitive silver halide emulsion layers having different speeds wherein the faster green-sensitive emulsion layer and faster red-sensitive emulsion layers are located further from the support then the slower green- and red-sensitive layers. The faster red- and green-sensitive layers can be relatively "starved" with respect to their color coupler contents in order to improve the granularity of these layers.
U.S. Pat. No. 4,186,011 discloses a color photographic material containing several differently sensitized silver halide layers, each of the three spectral regions having at least one silver halide emulsion layer, at least one of the spectral regions having at least three layers, one of which is free of silver halide but contains color coupler.
U.S. Pat. No. 4,564,587 discloses a light-sensitive silver halide color photographic material having at least one light-sensitive layer constituted of a plurality of silver halide emulsion layers of the same color sensitivity, the low sensitivity silver halide emulsion being closest to the support, the high sensitivity silver halide emulsion being farthest from the support and the medium sensitive layer being in the middle, wherein a non-sensitive intermediate is coated between the low and medium sensitive silver halide emulsion layers.
U.S. Pat. No. 4,704,350 relates to a silver halide color photographic material containing a pyrazoloazole magenta coupler to prevent color stains during development. Various multi-layer structures are disclosed.
U.S. Pat. No. 4,770,987 relates to a silver halide color photographic material at least one silver halide emulsion layer having dispersed therein lipophilic fine particles containing an image dye forming lipophilic coupler and further containing a lipophilic compound having a water-solubility of not more than 1% by weight at 25.degree. C. Various multi-layer structures are disclosed.
These references illustrate the development of color photographic elements and the movement toward more light sensitive photographic materials. Such materials have relied upon larger silver halide grain size to provide increased light sensitivity. The larger grain size of silver halide provides a problem. This problem is the increase in granularity, especially increased RMS granularity, that is observed in the photographic elements. Attempts to solve this problem have included use of multiple layers, such as described in the above references, and coupler starvation, such as defined in U.S. Pat. No. 4,946,765 (column 2).
Color photographic silver halide elements typically contain a layer unit sensitive to the blue region of the electromagnetic spectrum, a layer unit sensitive to the green region of the electromagnetic spectrum, and a unit sensitive to the red region of the electromagnetic spectrum. Each of the layer units can comprise one, two, three or more layers. At least one of the layer units typically comprises a layer that is the most light sensitive layer of the particular unit and designated the "fast layer" (FL); a layer that is the least light sensitive layer of the particular unit and designated the "slow layer" (SL); and, optionally a layer that has a light sensitivity between the light sensitivities of the fast layer and the slow layer, designated the "mid layer" (ML). For a given layer unit, the concentration of dye-forming coupler in each of the fast layer and the mid layer are typically within the range of 5 to 25% of the concentration of dye-forming coupler in the slow layer. This typical use of a limited concentration of dye-forming coupler in the fast layer and the mid layer enables coupler starvation as known in the photographic art. This use of coupler starvation also enables improvement of granularity of the photographic element at moderate and/or high exposure levels.
Until now, the color negative photographic silver halide elements that used coupler starvation were in a light sensitivity range that required the use of silver halide emulsion grains that were of such a size that the RMS granularity was controlled by the emulsion grain size and coupler availability. The normal coupler dispersion particle size did not limit the granularity improvement in such materials. However, a problem was encountered with photographic silver halide elements that were designed to be color photographic silver halide negative working duplicating elements, for example color motion picture duplicating films. The problem encountered was that the desired degree improvement in granularity could not be provided by coupler starvation alone and no answer to the problem was clear from the prior art.
This problem is particularly bothersome in the motion picture industry wherein multiple numbers of duplicates are prepared for distribution from a negative working duplicating element especially prepared for this purpose.
A continuing need has existed for a color photographic silver halide negative working duplicating element and particularly a negative working duplicating element for preparing positive motion picture prints having extremely low granularity.